This invention relates generally to filtration beds, and more specifically to adsorbent filtration beds of the type used in radioactive-gas filtration systems.
In the manufacture of adsorbent filtration beds, such as those including charcoal or silver zeolite, which are used in radioactive-gas filtration systems, one requirement is that a close tolerance of spacing between screens, or perforate sheets, which comprise the beds be maintained. The perforate sheets are often as wide as 31 inches so that reinforcing is required to give them structural rigidity and to maintain desired spacing tolerances.
Generally, this is done by putting Z-bar stiffeners in the beds as is depicted in FIG. 1 and described below. The perforate sheets are spot-welded to the end sections of the Z-bar stiffeners. However, a problem with using Z-bar stiffeners is that the end sections thereof create blank areas on the screens which are undesirable because they necessitate making the filter beds larger than is necessary to have the required surface areas. Thus, it is an object of this invention to provide stiffeners for giving rigidity to perforated sheets or screens of filtration beds and for maintaining spacings therebetween which do not create blank areas.
It is known in the prior art to employ pleats, or folds, in screens to space the screens from one another, such an arrangement being disclosed in U.S. Pat. No. 3,344,590 to Smith et al. However, heretofore, the use of such pleats has been limited to spacers and they have been mounted at lateral edges of filtration members. It is yet another object of this invention, therefore, to employ pleats in such a manner that they add rigidity to otherwise flat perforate sheets of filtration beds across unsupported spans thereof.